"The truth is, I'm not getting up an hour earlier and walking on a treadmill. I have the greatest workout partner in the world. And you don't need a gym membership for that kind of workout," femalefirst.co.uk quoted the 37-year-old actor.

Sudeikis, who began dating the 29-year-old actress in November 2011, has also made a number of changes to his diet.

"A lot of it comes from tiny things, like not eating barbecue sauce with my pizza at two in the morning. I think it's all a manifestation of being happy and wanting to treat myself well," he said.